Referring to FIG. 31, there is illustrated a conventional mounting system generally indicated by reference numeral 1. In general, the system 1 includes a supply section 2 for supplying electric components, a placement head 3 for receiving a component from the supply section 2 and then mounting the component on a substrate such as a circuit board, a transport unit 4 for transporting the placement head 3, a recognition device 5 for taking a digital image of the component held by the placement head 3, a holding section 6 for receiving and holding the substrate onto which components are mounted, and a controller 7 for controlling an entire operation of the system 1.
In operation of the system 1, the placement head 3 moves to a predetermined position above the supply section 2 bearing a component supply cassette 11, for example, with a number of components 12. A vertically extending vacuum nozzle 13 in the form of a quill supported by the placement head 3 is moved down to receive a component 12. The placement head 3 is then rotated about a vertical axis, i.e. Z-axis, by an angle controller 14 so that the component is oriented in a predetermined direction. The recognition device 5 takes an image of the component 12, supported by the nozzle 13 of the placement head 3, moving past a predetermined position opposing the recognition device 5. The image is transmitted to an image processor 20 where the image is processed according to a specific image processing technique to determine a position of the component, i.e., its horizontal and/or angular displacement relative to the nozzle. Information indicating the position of the component is transmitted to the controller 7. Based upon the information, the controller 7 corrects the position of the component. Then, the nozzle 13 is moved above a predetermined placement position of substrate 18 and then down toward the substrate 18 so that the component 12 is mounted on the substrate.
FIG. 32 is a flowchart showing a conventional method for mounting components. In this method, at step S1101, nozzle 13 receives component 12. Then, at step S1102, recognition device 5 takes a picture of the component 12 held by the nozzle 13. The picture is processed at image processor 20. A position of the component 12 is determined at step S1103 so as to determine whether the component 12 can be mounted on substrate 18. If the component 12 is incapable of being mounted on the substrate, the nozzle 13 brings the component to a collect station (not shown) at step S1106. Otherwise, horizontal and/or angular displacement of the nozzle 13 is determined at step S1104. Using this determined displacement, a horizontal position of the placement head 3 and/or an angular orientation of the nozzle 13 is adjusted. Finally, the component 12 is mounted in position onto the substrate 18 at step S1105. During this process, no judgement is made as to whether the nozzle 13 interferes with one or more components already mounted on the substrate 18.
In the meantime, electric devices are likely to be small sized and light-weight, thereby increasing a density of components mounted on substrate 18 considerably. For example, a clearance between neighboring components of about 1.0 mm×0.5 mm is decreased to about 0.2 mm. Notwithstanding this, each component should be mounted on the substrate so that it does not interfere with another component already mounted on the substrate. To this end, used is a nozzle with a tip end designed to be larger than a small component 12.
However, where clearance of components is down to about 0.1 mm, for example, a displacement of component 12 relative to nozzle 13 may result in an interference between the nozzle 13 and the component 12 already mounted on the substrate 18. This is illustrated in FIGS. 33A and 34B. In each drawing, illustrated are nozzle 13 and components (12, 12a) both viewed from a substrate. Specifically, in FIG. 33A, the nozzle 13 is shown so that it is angularly inclined relative to the component 12. In this instance, using an image of the component captured by recognition device 5 and a result obtained by image processor 20, controller 7 corrects a horizontal and/or angular position of the component 12 relative to the nozzle 13 before mounting of the component 12 so that the component is placed at a predetermined, correct position on the substrate. However, as shown by hatched lines in FIG. 33B, a part of the nozzle can result in an interference with another component 12a already mounted on the substrate. On the other hand, FIG. 34A shows a nozzle and component retained by the nozzle in which the component is horizontally offset from a center of the nozzle. In this instance, as shown in FIG. 34B, nozzle 13 is displaced so that the component is mounted at a correct position on the substrate, and this in turn results in an interference with another component 12a already mounted on the substrate as shown by hatching.
Although not clearly shown in these plan views, i.e., FIGS. 33B and 34B, since the component has a certain height, interference may be more problematic for a case with a reduced clearance when considering a deviation of height and/or inclination of the component. That is, interference between nozzle 13 and component 12a results in another displacement of the component 12a. What is worse, component 12 may be damaged, which results in a deterioration and/or malfunction of a circuit.